Burner and soaking pit



Nov. 19, 1968 K. A. GMI-:1.1.

BURNER AND SOAKING PIT 4 Sheets-Sheet 1 Filed Dec. 19. 1966 INVENTOR.

KARL. A 1 GMELL BY M las Agen'l Nov. 19, 1968 K. A. GMELL BURNER AND SOAKING PIT 4 Sheets-Sheet 2 INVENTOR. KAR/ A. GME LL F/Gy. 3

Agent K. A. GMELL BURNER AND SOAKING PIT 4 Sheets-Sheet 5 Nov. 19, 1968 Filed Dec. 19, 1966 INVENTOR.

(PR/0R ART) KARL A GMELL BY @MSNM Agent Nov. 19, 1968 Filed Dec. 19, 1966 MB TU PER TON TONS PER HOUR K. A. GMELI.

BURNER AND SOAKING PIT 4 Sheets-Sheet 4 TRACK TIME /N HOURS FIG. 7

TRACK TIME IN HOURS Ej-@ Q INVENTOR.

Agent KARL A. GMELL United States Patent O 3,411,761 BURNER AND SOAKING PIT Karl Alexander-Gmell, Hamilton, Ontario, Cmlada, as-

signor to The Steel Company of Canada, Limited, Hamilton, Ontario, Canada, a company of Canada Filed Dec. 19, 1966, Ser. No. 602,954 14 Claims. (Cl. 263-40) ABSTRACT F THE DISCLOSURE An improved burner for use in soakin g pits and furnaces comprising the combination of a port block and burner body having an axial port extending therethrough and an annular bafe formed in the burner body extending in the port whereby combustion air entering through the port is entrained by fuel jetted tangentially into the port downstream of the baie and obliquely into the soaking pit or furnace. The combustion products enter the soaking pit or furnace with a swirling motion to effectively heat the contents therein while permitting the formation of a protective layer of air at the top of the pit or furnace.

This invention relates to an improved burner and is particularly directed to a burner for use in bottom tired soaking pits for heating steel ingots.

The heating of steel ingots in a bottom fired soaking pit normally is accomplished by means of a single burner located in the center of the pit Hoor providing necessary heat requirements, the burner utilizing a low B.t.u. gaseous fuel which is introduced through a nozzle positioned in the center of a refractory burner port. Preheated combustion air is conducted to the pit in proximity to the burner from preheaters such as tile recuperators for combustion with the fuel discharging from the burner nozzle. The fuel and air are mixed by entrainment of combustion air in streams of gas discharging from burner nozzle openings and the products of combustion from the resulting mixture are directed upwardly for impingment against the underside of the closed pit cover, as is typified in the disclosure of United States Patent No. 2,563,683, In that a positive pressure is maintained in the upper half of the pit chamber under normal and controlled pit operating conditions, a portion of the hot combustion gases directed against the pit cover escapes to the atmosphere by diffusion through the sand seal which surrounds the periphery of the pit cover. The remaining combustion gases are deflected by the pit cover and pit draft to envelop the ingots in their downward course towards the gas outlets located at the lower parts of the opposed side walls of the pit.

This flow pattern in conventional soaking pits with direct impingement of hot combustion gases on the pit cover results in the cover being overheated with attendant high heat losses by radiation. It also results in the ingots being heated from the top down by a single passage of the heated combustion gases through the pit and has been found not completely satisfactory in that overheating of ingot surfaces directly exposed to the hot gases occurs because of restricted movement of the hot -gases Within the pit. Also, poor combustion efficiency because of limited mixing of fuel and air necessitates the use of a considerable excess of combustion air which severely adds to the oxidizing conditions in the pit, especially in the overheated regions, with resulting thick oxide scales being produced on the ingots.

Efforts have been made to overcome the above disadvantages in the operation of bottom fired soaking pits resulting in the development of mechanically complex diffusion-type burners for top firing soaking pits as described "ice in United States Patent No. 3,209,808. These top fired soaking pits, however, require a heat exchange system which can supply combustion air under relatively high pressure. Standard low pressure recuperators are not satisfactory for use as heat exchangers in top fired systems and top firing burners accordingly cannot be readily incorporated into existing systems without considerable capital expense and extensive structural modifications. In addition, top fired systems have not -been completely satisfactory in providing uniform heating of ingots since the source of heat i-s not equidistant from the ingots to be heated, the single or double burners being positioned in the tops of one or two side walls of the furnace.

I have discovered that the foregoing problems can be substantially overcome and that ingots can be heated to an even surface temperature and uniformly soaked throughout at a faster rate than heretofore accomplished in a bottom fired `soaking pit by utilization of the burner of the present invention. The present burner is capable of producing a uniform admixture of air with a gaseous fuel in a novel flow pattern which upon combustion provides a swirling, ring-shaped mass of hot gases which effectively envelops all sides of ingots positioned in said soaking pit for uniformly heating said ingots from the bottom upwardly and with inhibition of ingot washing or hot spots. I have more particularly discovered an improved burner for heating ingots which comprises, in combination, a circular port block and a burner body formed concentric and integral with each other and having an axial port therethrough for extension into the pit, an annular refractory in the shape of an inverted frustum of a cone formed in the wall defining said port, said annular refractory having a plurality of circumferentially spaced tangential fuel openings the axial extensions of which are inclined into the furnace and substantially intersect to define an imaginary circle concentric with and contained within the said port, said annular refractory defining with said wall an annular passageway in communication with the fuel openings for connecting said fuel openings with a supply of fuel under pressure, and means for communicating the axial port with a supply of combustion air.

It is a principal object of the present invention, therefore, to provide a burner simple in construction which can be incorporated in existing bottom fired soaking pits and which will effectively admix air With fuel for generation of hot combustion gases in a novel ow pattern for optimum production and distribution of heat in soaking pits.

It is another important object of the invention'to provide a burner having a self-regulating fiow pattern of heating ygases with flame stability during burner turn-down and during cold wall conditions.

Another object of the invention is the provision of a burner which Aminimizes pit hot spots and overheating for an extended refractory life necessitating less frequent shutdowns for maintenance and bottom digging.

And another object of the invention is `to provide a burner which will permit quick and uniform heating of ingots in a soaking pit with a minimum of excess combustion air requirements to minimize oxidation of said ingots during exposure to heating gases.

These and other objects of the invention, and the manner in which they can be attained, will become apparent from the following detailed description of the drawings, in which:

FIGURE 1 is a cut-away perspective view, partly in section, illustrating the burner of the invention located in its operative position in a soaking pit and showing schematically the flow pattern of gaseous combustion products therein;

FIGURE 2 is a section along the lines 2 2 in FIGURE 1 showing in more detail the construction of the burner of the invention and fuel-air flow in proximity to the burner;

FIGURE 3 is a plan view taken along the line 3-3 in FIGURE 2 showing the disposition of tangential fuel outlets;

FIGURE 4 is a plan view of the burner showing the fuel ow pattern proximity to the burner;

FIGURE 5 is a vertical section taken across FIGURE 1 showing the general ow of hot combustion gases within the soaking pit;

FIGURE 6 is a vertical section through a bottom fired soaking pit having a conventional burner and illustrates the flow pattern of combustion gases therein;

FIGURE 7 is a graph illustrating improvement in pit tonnage for a 65 ton average charge weight using the burner of the invention compared to the use of conventional burners; and

FIGURE 8 is a graph showing improvement in fuel utilization for a 65 ton average charge weight using the said burner of the invention compared to the use of conventional burners.

Like reference characters refer to like parts throughout the description of the drawings.

With reference to FIGURES l through 5, the burner 10 of the invention is positioned in the centre of the door 12 of a soaking pit having side walls 13 and removable cover 14. The oor 12, walls 13 and cover 14 are lined with a refractory and reinforced with structural steel. The openings 15 communicating the soaking pit chamber With a low-pressure recuperator system, not shown, are provided in the lower parts of the opposed side walls 13.

Burner 10 generally consists of port block 16 having annular section 17 elevated above the plane of floor 12 and annular flange section 19 extending downwardly and outwardly into said oor co-planar with the floor surface. Port block 16 is formed integral and concentric with burner body 20 which extends downwardly through the pit floor 12. The axial port 22 formed vertically within port block 16 and burner body 20 is enlarged by annular recess 24 to receive a plurality of refractory segments 26 which collectively are in the shape of an inverted frustum of a cone at their lower portions 23 and in the shape of a cylinder at their upper portions 25, as will be discussed in more detail below. The burner body 20 is stepped inwardly to provide a ledge 29 to support refractory segments 26. Port 22 extends at one end into the soaking pit at port block section 17 and is in communication with air conduit 30 at its opposite end. Annular passageway 33 dened by refrac-tory segments 26 in recess 24 is cornmunicated with fuel supply conduit 34 by a pair of interconnecting ducts 36.

Turning now to FIGURES 2 and 3 in which the structure of the invention is shown in more detail, the fuel supply conduit 34, the pair of opposed ducts 36 extending laterally outwardly and upwardly from duct 34, and the manifold 37 connected to the upper extremities of ducts 36 defining annular passageway 33 are formed of steel plate welded together to form a rigid and substantially gas-tight assembly 50.

Refractory bricks or the like heat resistant material 58 form the interior and exterior walls of burner body 20 and dene tunnel 30 which receives preheated combustion air from the recuperator system. Heat resistant key bricks 28 supported by refractory bricks 58 and by brackets 51 welded to the inner walls of ducts 36 are stepped inwardly t0 provide the annular ledge 29. An annular ange 31 projecting inwardly from the base of manifold 37 is co-extensive with ledge 29 and abuts the upper surface thereof.

A pluraltiy of refractory segments formed of tile having a minimum of expansion and contraction characteristics are seated upon flange 31, the base of the refractory segments being planar to abut ange 31 and the rear wall surface 32 being arcuate to abut the inner wall of manifold 37. The top of refractory segments 26 is planar to receive annular steel plate 27 which is continuously welded about its outer periphery to the top surface to manifold 37 to form a gas-tight enclosure at the rear of the refractory segments. Steel wear plate 40 is seated upon plate 27 and the upstanding edge 41 of manifold 37 wear plate 40 preferably being segmented and each segment tack welded to manifold edge 41 on its outer periphery and loosely resting on plate 27 on its inner periphery. Each segment is spaced from the adjacent segment to provide a plurality of radial slots or keyways for reasons which will become apparent as the description proceeds. Bedding mortar preferably is used to provide a tight seal between refractory segments 26 and the steel manifold 37, the underlying flange 31 and the overlying plate 27.

Refractory segments 26, each comprising in the present embodiment one-sixth of a circle for ease of fabrication, installation and replacement, together provide an inverted frustum shaped portion 23 extending inwardly into port 22 to define an annular bafe 42 and a cylindrical shaped portion 25 extending upwardly co-planar with the inner surface of port block 16. A plurality of tangential fuel openings 44 having straight axes which will extend upwardly obliquely into the pit above lthe edge of the port block are circumferentially spaced about the refractory segments 26 to substantially intersect at an imaginary circle designated by numeral 46, shown in FIGURE 4 to be concentric and co-extensive with the innermost edge of annular baffle 42. Openings 44 lterminate at one end in port 22 at the annular recess 47 formed about the inner surface of refractory segments 26 in proximity to the junction of the inverted frustum shaped portion 23 and the cylindrical shaped portion 25 and terminate at the other end in alignment with openings formed in the inner wall of manifold 37.

The port block 16 formed of a moldable refractory such as chrome ore plastic is seated upon wear plate segments 40 and plate 27 and is keyed in its operative position by the keyways defined between the said segments. A reinforcing ring 61 denes the upper outer periphery of section 17 which extends into the pit. Lower peripheral flange 19 formed integral with section 17 overlaps the outer upper portion of manifold 37, flange 19 extending outwardly into floor 12 of the pit.

The upper surface 63 of port block 16 is bevelled inwardly as illustrated in FIGURE 2 such that the plane of said surface is substantially parallel to the axes of refractory segment openings 44.

In operation, a gaseous fuel under pressure is fed to the yburner by means of conduit 34 and distributed to the passageway 33 in manifold 37 via ducts 36 and thence to the openings 44 in refractory segments 26 through manifold holes 60. The fuel is jetted tangentially through openings 44, the upward inclination of the openings permitting the jets of fuel to `clear the upper surface of section 17 of port block 16. Because of the tangential discharge of the fuel, the jets intersect for impingement on each other at the imaginary line designated by numeral 46 in FIGURE 4 and are deflected in a clockwise direction to impart a swirling motion to the gas. The innermost central portion of port 22 is maintained free of turbulence permitting a .column of air 64 to rise vertically in the furnace and form a relatively cool layer 66 across the top of the furnace as shown in FIGURE 5. Air in the periphery of the rising column of air is constricted by annular `baffle 42 formed by ledge 29 and refractory segments 26 to produce a venturi'effect in proximity to the fuel jets as the air rises past the fuel openings, thereby enhancing entrainment of the air by the fuel jets.

The mixture of gas and air forms a swirling sheath of combustion gases 65 upon ignition, as shown in FIG- URE 2, which spreads out laterally in the furnace to envelop thel ingots at their lower extremities and rise along the sides of the furnace 'with continued swirling motion to completely envelop the remainder of the ingots. The hot combustion gases are then deflected inwardly towards the centre of the furnace and roll downwardly and outwardly for discharge through outlets leading to a recuperator system. FIGURE 5 illustrates this ow pattern of heating gases in a pit employing the present invention compared to the conventional flow pattern heretofore provided by prior art burners, the latter shown in FIGURE 6. Air column 64 rising vertically in the pit supplies air to the roof of t-he pit Where the air spreads out laterally to provide the relatively cool layer 66. This is verified by analyses made across the pit of the products of combustion immediately under cover 14 which indicate a consistent average of, for example, 5% unconsumed air with the presence of no combustible gases. Conventional pits on the other hand, although normally having a greater excess of combustion air supplied to the pit, often will discharge unburned gases from the pit cover which will support a ame indicating the absence of combustion air in this location of the pit.

The burner of the invention provides a number of other important advantages. FIGURES 7 and 8 illustrate the significant increase in productivity 'with attendant decrease in fuel consumption which has been obtained by use of the burner in a bottom fired soaking pit having a charge weight of 65 tons of steel ingots. Oxidation of ingot surface is substantially reduced and soaking of the ingots is rapidly and uniformly effected to achieve the desired Working temperature. In that combustion air requirements are reduced due to the efficiency of the burner, preheated air temperatures can be increased as much as 200 F. above the temperatures normally obtaine-d.

Although the description of the burner of the invention has proceeded with reference to its use in soaking pits, it is contemplated the burner can be utilized in furnaces such as `blast furnace stoves, boilers and the like furnaces which utilize 'gaseous fuels wherein it is desired extensive and uniform coverage of heating products of combustion be obtained.

It will be understood, of course, that modifications can be made in the preferred embodiment of the invention described and illustrated herein without departing from the scope of the invention as defined by the appended claims.

What I claim as new and -desire to protect by Letters of Patent of the United States is:

1. A burner for use in a soaking pit or the like comprising, in combination: a port block and burner body having an axial port extending therethrough intothe pit for the supply of combustion air; an annular bafile formed in the inner wall of the burner body extending into the port; said burner body having a plurality of circumferentially vspaced tangential openings formed therein downstream of said bafe and inclined obliquely into the pit, the axial "linear extensions of said tangential openings substantially intersecting to `define an imaginary circle concentric with and contained within the port; an annular manifold formed in said burner body having a plurality of openings in communication with said tangential openings; and duct means for communicating said annular manifold with a supply of gaseous fuel under pressure.

2. In a burner as `claimed in claim 1, said port bafiie and said tangential openings defined by a plurality of refractory segments removably secured to said burner body adjacent the annular manifold.

3. In a burner as claimed in claim 2, said refractory segments having an -upper portion cylindrical in shape and substantially planar with the inner wall of said block and a lower portion in the shape of an inverted frustum of a cone defining the annular baie, the tangential fuel openings being disposed in said refractory segments in proximity to 'the junction of said cylindrical upper portion and the portion in the shape of an inverted frustum of a cone.

4. In a burner as claimed in claim 3, said manifold and duct means formed of steel.

5. In a burner as claimed in claim 4, a steel wear plate formed of arcuate segments seated on top of said manifold, said arcuate segments being spaced apart to define a keyway 'between each adjacent pair of segments for receiving the port block in locked engagement.

6. In a burner as claimed in claim 3, said port block being centrally disposed in the soaking pit or the like fioor and extending upwardly into the furnace above the said floor.

7. A burner for a soaking pit or the like comprising in combination: a circular port block and a burner body forme-d concentric and integral with each other and having an axial port therethrough for extension into the pit; refractory segments collectively in the shape of an inverted frustum of a cone formed in the wall defining said port, said refractory segments having a plurality of circumferentially spaced tangential fuel openings the axial extensions of ywhich are inclined into the furnace and substantially intersect to define an imaginary circle concentric with and contained within the said port; and said refractory segments defining with said Wall an annular passageway in communication with the fuel openings for connecting said fuel openings with a supply of gaseous fuel under pressure.

8. In a burner as claimed in claim 7, said refractory segments having an Vupper portion cylindrical in shape and substantially planar lwith the inner wall of said block, the tangential fuel openings being disposed in Said refractory segments in proximity to the junction of said cylindrical upper portion and the portion in the shape of an inverted frustum of a cone.

9. In a burner as claimed in claim 7, said refractory segments having an upper portion cylindrical in shape and substantially planar with the inner wall of said block, the tangential fuel openings being disposed in said refractory segments in proximity to the junction of said cylindrical upper portion and the portion in the shape of an inverted frustum of a cone and terminating at one end in an annular recess formed about said refractory segments at the said junction.

10. In a burner as claimed in clairn 3, said refractory segments defining an annular baffle within said port.

11. In a burner as claimed in claim 10, said imaginary circle having a diameter substantially equal to the diameter of said port bafiie.

12. In a burner as claimed in claim 10, means for communicating the axial port with a supply of combustion air.

13. In a burner as claimed in claim 7, said port block formed of a refractory material and having its upper surface bevelled inwardly such that the plane of the upper surface is substantially parallel to the axis of each diametrically opposed fuel opening.

14. In a -burner as claimed in claim 13, said port block being centrally disposed in the soaking pit or the like floor and extending upwardly into the furnace above the said floor.

References Cited UNITED STATES PATENTS JOHN I. CAMBY, Acting Primary Examiner. 

